Upper and lower limit switch mechanism for electrical hoists



Jan. 6, 1931 w. A. HUMMEL 1,785,302

UPPER AND LOWER LIMIT SWITCH MECHANISM FOR ELECTRICAL HOISTS Filed Oct.31, 1927 3 Sheets-Sheet l a E @L y ii veicZ' ozw %Mazwej A y dl ivzeyqJan. 6, 1931. w. A. HUMMEL 1,788,302

UPPER AND LOWER LIMIT SWITCH MECHANISM FOR ELECTRICAL HOISTS Filed Oct.31, 1927 3 Sheets-Sheet 2 I l I I I l 1 I I I 1 l I zweznnri Jan.6,1931. HUMMEL 1,788,3@2

UPPER AND LOWER LIMIT SWITCH MECHANISM FOR ELECTRICAL I IOISTS FiledOct. 51. 1927' 3 Sheets-Sheet 3 Patented Jan. 6, 1931 'rrEe STATES P T-CE WILLARD A. HUMMEL, or PHILADEL'PHIA, PEN SY VANIA,AssIGNoitfToAMnnIoAN ENGINEERING COMPANY, or PHILADELPHIA,ianNNsYLvriNiA, A CORPORATION or PENNSYLVANIA nrPER'ANn LOWER LIMIT swircii MEcirA i sivi: ron amn on. HOISTS/ a 7 plication filed mm 31,15,271, seria Ne. 236,111.

My invention relates to systems ofjcontrol for hoisting apparatus andthe like.

stall limit-switch mechanism inthe pilot cir- 5 cuitof hoistcontrol-equipment. The pilot circuit functions as an auxiliarycircuit tothe main iiiotor-energizingcircuit, and it in cludes in addition to, thelimit-switch mechanism, the push-button station which is controlled bythe operator and also the energizing windings of the .contactors in themain ,inotor circuit. Such arrangement, however, has not proved entirelsatisfactory in practice. For example, the contact pointsof the maincontactorequipment very frequent- 1y fuse together, thereby permittingthe continued energization of thezdriving motor,"

by the limit-switch mechanism.' .7 p

An object of my invention, therefore,is to provide a system of controlwhich overcomes thedisadvantages characteristic of the pilotcircuitequipment,my invention contemeven though the pilot circuit has beenopened plating the insertion of the limit-switches rectly in the mainmotor circuit. V

. Another object of my invention is to provide mechanism of'thecharacter described,

wherein the positiveactuation of the limitswitches 1s assured by powerderived from the hoisting drum; and wherein damage to the switch mechansm is averted upon aypredetermined over-travel of the drum:

A further object of myinvention is toprovide a stop mechanism comprisinga driving tion connection therewith, a third member adapted to beconnected to the limit-switches, a fourth member, a wheel carried by thefourth member in such operative relation to the driven member as to beactuated bodily upon the initial movement of the driveninemmy'invention;i i ,1. Y i Fig, .is'an enlarged detail horizontal sectional view of thestop mechanism shown in member, a driveii'member having alost-mopracticed, will be apparent more fully here inafter, When't'akenin connection with the accompany ng drawings, wherein, It hasheretoforebeen the practice to in- Figjl 's a top plan view, partiallyirihorii zoi'ital section, of one form of embodiment of Fig. 1, thesectional plane being takenon the Figs. 3 and-.4; are endand sideelevatio nal v ews, respect vely, of the structure shown in Fig. 2, the'severalparts being shown in Referring] to L'the mono-rail hoist the-reinshown comprises-a driving electric motorljra drum 2, which ismounted ona shaft 3;',gearing at which extendsibetween the motor 1 and'one end 50fa-drum shaft astop mechanism 6 which is operatively as sociated withjaniopposite end? of the drum shaft 3; and a pair of limit-switches 8and 9.

As shown in 5', these switches are respectively connected in conductorsHand 12,, which constitute a divided circuit portion of a 'main motorenergizing circuit 13. The conductors lland 12- are connected toa pairof reversing jcontactors which serve to controltlie'direction ofoperation of the motor 1, andinay be controlled from a remote "point bythe usual push-button station The latter, as well as the reversingcontactors, havenot beenshown in order to simplify the description of myinvention, it being deemed sulficient to vspecifymerely that whencurrents "are'supplied to the branch conductor portion 11 of theenergizing circuit 13,

the motor 1 operates, say,1in"a directionto lift the hoisting hoolgandthat when currentsjare s'uppliedto the branch conductor porti on.12,fthe motor 1 is so energized as to operate in the opposite direction,that is, in a. direction tending to lower the hoisting hook, The limitswitch]9,therefore,must' be closed in order for the motor to raise thehoisting hook, and the switch 8 must be closed for the motor to lowerthe'hook; and thisis the nor'mal position of these switches, all as Wi lappear more fully hereinafter.

LOU

Considering in I greater detail the stop mechanism 6, a shaft section 14is provided with an enlarged head portion 15 which is adapted to bedetachably secured to the end portion 7 of the drumshaft3 in anyconven-- ient manner; rocker frame or flier 16 is provided at one endwith an enlarged portion 17, which is journaled on an adjacent portion.18 ofithesh'aft sect-ionl i, and. a sleeve portion-19 which'gextends'from'the'portion 17 into abutting relation to a shoulder 21 formed bythe shaft head portion 15. An opposite end 22 of the'roclrer frame 16 isprovided with a journal portion '23 which is mounted on an adj acent-shaftportion 24of reduced diameter. A shoulder 25, which is positioned atone end of the shaft'portion 18,

afi'ords an abutment tending to prevent a movement of the frame16=toward thejdrum' shaft 3. The movement of the frame 16 in theopposite direction may be preventedby a nut 26 which is mounted on athreaded end portion 27 of the shaft portion'24.

A portion28' of the shaftlsection 14 tween the bearing portions "18 and24 there" of, is threaded for the reception of a travelingnut or crosshead. 29 and a pair of adjustably spacedclutclrcollars 31 and 32. Thespacing between the collars 31 and 32 is such thatthe drum'g2 may bemoved through its maximum distancebefore a shoulder'33on the travelingnut 29 engages a shoul- 'der 34 on one of the collars 31, 32. 7 Sincethe travelingnut 29 is connected at the upper I and lower edges thereofby shoulder portions 35 and-36 to spaced parallel side portions 37 and38 of the rocker frame 16, thecontinued turning of the drum shaft 3andconsequently the shaft-section 14 causes a corresponding movement ofthe rocker frame 16. Thus, the rocker frame116 is actuated only when thetravel of thedrum 2 exceeds a'certain value which has been predeterminedby the spacing ofthe collars 31 and 32. V

The rotatable frame 16 may be returned to its initial position .showninFig. 2 of the drawing, when the traveling nut 29 disengages either ofthecoeacting clutch collars '31 and 32' due to the reversal of the drum '2,by means of a spring 39 which encircles the rocker frame portion 16. Asshownin Fig. 4, opposite ends 41 and 42 of the centering spring .39 arepositioned'on opposite sides of'lugs or shoulders 43 and 44. The lug 43extends from a vertical base plate '45 which is secured to an adjacentportion 46 fof the hoisthousing in any convenient manner. The lug 44issecured to the rocker frame 16, and it is disposed between thePortions of the spring ends 41 and 42 which are positioned intermediatethe, .shoulder43 and the rocker frame portion'16L Hence,

t'heroclrer frame-or flier. constitutes a float- ,l g, sprung-centermember with a lost-motion connection to the .d-rnn shaft I In accordancewith my invention, movement of the floating rocker frame 16 frompreferably provided with a beveled portion 53 having angled sides54and55 terminating in a central peripheral edge 56. The enlargedportion 17Zof the floating rocker frame 161s provided with acomplementary circular recess or groove 57, which is adapted to receivethe beveled port1on53 of the wheel 48 and which constitutes acirculartrack in' frictional engagement. therewith.

As shown 1n 'Flg. 2, the c rcular groove 57 isprovided with an enlargedrecess portion 58 which is. adapted to receive an adjacent portion '59of thewheel 48,. affording aseat therefor, ,The position of the recessportion .58 is, suchthat the wheel 48 is seated thereon only when therocker frame 16'is in the central position shown in the drawing. Shouldthe rockerframe16 turn in either direction, then the wheel 48 isactuated out of the recess portion 5.8 duringthefinitial movementlpf therocker frame 16'and thereafter it traverses the remaining track portionof-the groove 57 without causing a further bodily-movement of the wheel48. There is thus. a lost-motion connection'bet'ween the rocker sleeveparts 47,48 and the floating frame 16. Therocker sleeve47 may be mountedon a shaft- 61,.oppositeends .62fand 63 of which are journaledin theloaseplate 45. anda plate portion .64 thereof. The movement oftherockersleevej47 may be transmitted toa;

switch operating member 65 through multi- 'ilying linkage .66 whichisso-designed that a relatively small movement of the rocker sleeve 47causes a relatlvelyj large movement of the switch operat ng member 65.As

illustrated in Fig.3,the linkagel66 com prisesfan arm67 extendingdownwardly from the-sleeve 47 afpairof links 68, andan arm 69 which isrelativelyshort comparedwith the arm 67 and which also {extendsdownwardly from the switch operating member 65. The

member 6.5 ,may be mounted on a shaft .71, opposite ends of which 'areournaled n a hub portion .72 of the base plate 45and the frame portion64. T V

Since it is --.desir able, for reasons .as will presently'appear, toreturn automatically theswitch operating member. 65 the wheel 48 and:the intermediateparts to theneutrgl position shown in the draw ng,'1mmed1ately upon the return of the rocker frame 1'6 .to. t s neutralposition, a centering .spring 73 is, mallnted on the hub portion 72 ofthe base plate 45. I .Qpposi e end Hand 7 .01.6 t Spring .73 .errsers-1aarsewaswere track, of mechanism to be controlled, and

means for operativcly associating said meclianism and said drivenmembercomprising a rotatable element, the periphery of which is beveled,said track having acomplementary portion in frictional engagement. withsaid element. V V. i V

3. Stop mechanism for ho st ng apparatus comprising dr ving means,a'floating spr ng- .centered driven member havinga lost-motionconnection therewith, a. second member adapted to actuate switchmechanism, :and

means extending between-said members com prising a rotatable elementhaving a lost motion connection with said-driven member and linka eadapted to cause a rapid movement of said second member upon-theoccurrence of a relative 'movementbetween said element and saiddriv enmember.

4. Control apparatus fora hoist comprising driving means, afloatingspring-centered driven membenhaving a lost-motion connection therewith,a second spring-centered floating member adapted to actuate limit switchmechanism, and means whereby said second member may have a predeterminedmovement only upon'the initial actuation. of said driven member,rsaidmeans comprising multiplying linkage, a thirdrotatable member connectedto said linkageand an element positioned in frictional engagement ,with

said driven member and carriedbysai dthird member. e p

.5. Apparatus compr sing driving.mcans,a spr1ng-centered drivenmemberLhav ng a lost- 1notion connection therewith,, a secondspringrcentered member, a rocking .member,

means carried by said rocking member for causing a movement thereof'upona relatlve' movement between said rock ng member and said driven member,and movement-multiplying linkage extending between said rocking memberand said second spring-centered member. I p I 6. driving member, adriven member having a lost-motion connection} therewith, a

member also rotatable adaptedtoibe connected'to switch mechanism, afourth rotatable be actuated upon a predetermined movement of said nut,a thirdmember adapted "to be connected to switchmechanism, a fourthmember havinga rotatable mounting, an element carried by said fourthmember and positioned in frictional engagement with. said driven.member, andi linkage extending be? fourth member and said'th'irduponengagement of said nut with one of said I stops, a spring-centeredmember adapted to be connected to switch ',n1echanism, a fourth memberalso rotatable and'having such lostmotion connection tof'said drivenmember as to be actuated-thereby upon an initial movement of said drivenmember, multiplying means forfoperatively. associating said fourthmember and said third member, so that a quick movement. of the switchmechanism may occur upon said initial movement. i

9; In astopmechanism forhoists, the combination with a driving memberhaving a threaded portion provided with spaced stops and a travelingnut, of a spring-centeredfioating member so connected to said nut as tobe actuated upon engagement of either of said stops with said nut, saiddriven member having a'circular track, a second spring-centered floatingmember adapted toibe operatively associated with switch mechanism, afourth member havinga rocking support, an element U carried bysaidfourthmember and positioned in such operative relation to thetrackof said driven member as to be actuated bodily upon the occurrenceof a predetermined movement of said drivenmember, and linkage extendingbetween said fourth member and said second spring-centered member,whereby said bodily movement of the element may be imparted to saidswitch mechanism.

10. Apparatus of a character described comprising a driving motor, amain energizing'circuit for saidmotor having a divided portionrespectively including limit-switches, adrum actuated by said motoryandoperating mechanism for said switches efiective upon a predeterminedover-travel of said drum. 11. Apparatus of the character describedcomprising a drivingmotor having a main energizing circuit with adivided portion adapted to permit reversal in thedirection of operationof said motor, limit-switches for said divided circuit portion,respectively, a drum connected to said motor, and means for causing theoperation of oneor the other of said limit switches' depending upon thedirection of over-travel of said motor.

12. In combination, a driving motor,a'main energizing circuithaving adivided portion adapted to permit reversal in the direction of operationof said motor, normallv closed limit-sWitches fOr said divided circuit.portion, respectively, a 'drum'connected to be ac; tuated by said motor,and means responsive to over travel .of said drlnnin ei herilirectienfor causing the opening of at least one of said limit switches.

13. In a system of control for a hoist, the combination with a drivingmotor of a main energizing circuit for said motor having a dividedportion adapted to permit a reversal in the direction of operation ofsaid motor, normally closed limit-switches for said divicledcircuitfportio'n, respectively, a drum 1 actuated by said motor, andmeans responsive only to the initial over-travel of said drum forcausing the operation of one of said limitswitches. V

14. In apparatus of the character described, the combination with adriving motor and a main energizing circuit therefor provided with apair of limit-switches adapted to cause an interruption in the operationof the motor in either direction, of a drum actuated by said motor, andmeans for causing the operation of at least one of said switches uponthe overtravel of said drum, said means comprising a threaded shaftprovided with spaced stops 7 and traveling nut, a fioatingspring-centered. member havingsuch connection with said I nut as to beactuated thereby upon the engagement of said nut with either of saidspaced stops, a second spring-centered floating member adapted to beconnected to said limit-switches and means for operatively associatingsaid first-mentioned spring-centered member and saidsecond-mentionedspringcentered member so that at least'one of saidswitches may be actuated upon the voccurrence of a predeterminedmovement of said first-mentionedspring centered member.

WILLARD A. HUMMEL.

